Normal air diffusion reduces tire pressure over time. Hence, the usual state of tires is underinflated. Accordingly, drivers must repeatedly act to maintain tire pressures or they will see reduced fuel economy, tire life, and/or reduced vehicle braking and handling performance. Tire Pressure Monitoring Systems have been proposed to warn drivers when tire pressure is significantly low. Such systems, however, remain dependant upon the driver taking remedial action when warned to re-inflate a tire to the recommended pressure. It is a desirable, therefore, to incorporate an air maintenance feature within a pneumatic tire that will maintain correct air pressure within the tire without a need for driver intervention to compensate for any reduction in tire pressure over time.